The invention relates to footwear, namely the interior sole structures of shoes. In particular, the invention relates to constructions for use as an interior sole of a shoe, to wholly or partially suspend a foot above the base of the shoe, even during gait.
In recent years, the increasing popularity of shoes designed for enhanced comfort has led to a number of improvements to the insole structure of different types of shoes. Innovations in flexible cushioning materials, such as the development of molded ethylene vinyl acetate (EVA) outsoles and polyurethane foam insoles, have enabled manufacturers to provide a degree of shock attenuation in dress shoes typically reserved to athletic shoe designs. Integration of orthotic structures, such as heel cups, into shoes can also provide the wearer with better support and greater stability during gait.
Many such improvements have had their genesis in athletic shoe design. For example, the desire to enhance the performance capabilities of running shoes led to the development of midsoles with fluid or gas filled bladders embedded at strategic points for use in absorbing energy transmitted to the shoe during gait, and releasing it afterward (a recent iteration of the bladder technology is found in U.S. Pat. No. 5,987,780). A similar goal is targeted in shoes which include a trampoline-like structure incorporated into the heel and/or other regions of an otherwise cushioned midsole (see, e.g., U.S. Pat. Nos. 5,070,627 and 5,561,920). In the trampoline design, a grid formed of resilient fibers is stretched tautly beneath strike points of the foot, such as the heel. In both the trampoline and bladder designs, the energy return system acts like a spring, compressing on application of a force, then returning to its original shape on removal of the force.
While each of the aforementioned designs has its advantages, all also have limitations. For example, soft molded insoles and outsoles can become uncomfortable if their contours do not match those of the wearer""s foot. In the trampoline and bladder designs, the springiness which improves performance if used at discreet points in an otherwise conventional midsole design can cause the shoe to become unstable if added throughout the midsole. Foot fatigue is also an issue for all of these designs, which still rely on the foot to absorb and deflect a significant amount of the force generated during gait.
Further, customizability is largely lacking among existing shoe designs, most of which allow for little, if any, modification of the midsole by the wearer. As an alternative, one could use a custom designed orthotic device for insertion into a conventional shoe which addresses the wearer""s specific orthotic needs. However, such devices have limited adaptability to different shoe structures (e.g., most are not suitable for use in shoes with raised heels), and are usually expensive to purchase.
The invention provides shoes with an improved sole structure, as well as removable orthotic soles, which each overcome many of the limiatations of the prior art by suspending the foot above the base of a shoe. The invention also allows for relatively low cost manufacture of a lightweight shoe, by providing means by which the inventive sole and shoe upper may be manufactured as a unitary structure.
In all of the embodiments of the invention, the invention includes a hammock-like lattice which substantially conforms in topography to the foot, or a weight-bearing portion thereof (such as the heel or forefoot). Although the lattice may optionally contact or be incorporated with components which provide for energy return and cushioning, the principal role of the lattice is to support and control the position of the foot. This function is provided by suspending the foot slightly above the base of the shoe at all times, even during gait. In this manner, the suspended portions of the foot are largely protected from the shock which is transmitted upwardly from the ground during gait, and are gently supported while bearing a load, an especially useful feature when standing for a long period of time.
In one aspect, the invention consists of a shoe in which the lattice comprises the all or a part of the interior sole structure of the shoe (including the midsole and insole layers). The shoe further consists of an upper to encircle all or part of the wearer""s foot, and an outsole adapted to engage the ground.
In one such embodiment, the lattice is disposed within the shoe on a scaffolding consisting of an annular frame supported vertically by side pillars. In particular, a resilient annular frame is fitted along the inner perimeter of the shoe upper, and may optionally be secured by attachment means to the upper. The lattice is stretched between the sides of the scaffolding in the same plane as, but lying slightly above, the interior base of the shoe.
The frame is vertically supported in the shoe by a multiplicity of side pillars extending downwardly from the frame along the inner surface of the upper. Depending on the degree of vertical support required for the frame and lattice structure, the side pillars may also extend along the width of the insole liner to form xe2x80x9cUxe2x80x9d shaped structures, in which the bight of each xe2x80x9cUxe2x80x9d rests on the base of the shoe.
The lattice is preferably woven, molded or extruded to possess contours which conform substantially to the topography of the sole of a wearer""s foot. The lattice is also constructed of high tensile strength, low xe2x80x9cspringinessxe2x80x9d fibers (e.g., a polymer or lightweight metal) woven to form a mesh which deforms to the specific topography of a wearer""s foot. The fibers are stretched between the sides of the frame at a relative tension sufficiently low to allow desired portions of the lattice to deform on contact, but sufficiently high to maintain the foot in suspension above the base of the shoe.
Advantageously, the lattice is preferably provided with discrete regions having different degrees of elasticity, to provide control of gait. For example, the midfoot region of the lattice underlying the arch of the foot (medial midfoot) may be less elastic than adjacent regions of the lattice, to provide for control of supination (rolling inward) during gait. Such regions of varying elasticity may be provided by increasing the relative tension of lattice fibers within a given region, or by varying the composition of the lattice, as in providing a material of low elasticity along the medial midfoot region, and more elastic material in adjacent regions.
In one aspect of the inventive shoe described, the annular frame includes rotation means at varying points (e.g., at the forefoot and heel), to allow the frame to vertically bend to, for example, allow the frame to follow the curvature of the shoe upper and outsole.
In another aspect of the inventive shoe described, the side pillars include shock absorption means, such as a piston or closed cell foam bar.
In another aspect of the inventive shoe described, energy return and/or cushioning means, such as, respectively, an air bladder or polyurethane foam pad, are incorporated into the interior base of the shoe to contact the underside of the lattice at one or more strike points along the foot, or are incorporated within the lattice itself at such points.
In another aspect of the inventive shoe described, the upper, scaffolding and, optionally, the lattice are integrally formed as a unit.
In another embodiment of the invention, a shoe is provided in which a lattice is disposed substantially as described above, except that the annular frame only extends around the inner perimeter of the upper adjacent to one or more weight-bearing regions of the foot, such that only those region(s) of the foot are suspended in the lattice.
In another embodiment of the invention, the frame and lattice are constructed substantially as described above, except that the entire sole structure may be removed from the shoe for use as an independent orthosis.
In another aspect of the both the shoe and orthosis embodiments of the invention, the annular frame includes adjustment means which allow the user to increase or decrease the tension applied to the lattice at discreet points.
In another aspect of the both the shoe and orthosis embodiments of the invention, the lattice is attached to the annular frame along a removable annular ring, to permit the lattice to be repaired, replaced or substituted with a lattice of differing structural characteristics; e.g., for a lattices having different contours.
In yet another aspect of the invention, the lattice is formed as an integral part of the shoe upper. In this embodiment, the shoe upper supports the lattice, in lieu of the annualar frame, which is therefore absent.